Improvement in balanced slide-valves



J. C. BRYAN. Balanced Slide-Valves.

No. 205,723. Patented July 9,1878..

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UNITED STATES PATENT OEEIcE.

JOHN C. BRYAN, OF TITUSVILLE, PENNSYLVANIA.

IMPROVEMENT IN BALANCED SLIDE-VALVES.

Spe/rlication forming part of' Letters Patent N0. 205,723, dated July 9,1878, application tiledl Y April 29, 187e.

To all whom it may concern.:

Be it known that I, JOHN C. BRYAN, of .litusville, county ot' Crawford,and State of Pennsylvania, have invented or discovered 'a new and usefulImprovement in Balanced Slide-Valves; and I do hereby declare thefollowing to be a full, clear, concise, and exact description thereof,reference being had to the accompanyingdrawing, making a part of thisspecication, in which-like letters indicating like parts- Figure l is alongitudinal vertical sectional view of a steam chest, valve, and ports,illustrative of my improvement. Fig. 2 is a like view, showing the valvein a different position relative to its ports. Fig. 3 is a cross-sectionin the plane of the line m x, Fig. l; and Fig. et is a detached View, inperspective, of the valve, and showing the lower face ofthe relief orbalancing plate.

The side walls o' an ordinary steam-chest are shown at A, the bottom atAl, and the top plate at A2.

The steam-ports a a', of the usual or any known construction, lead tothe opposite ends ofthe cylinder. Steam is admitted from thesteam-generator at B, and passes into the valve by the port I). The livesteam admitted by this port passes alternately by ports c a to thecylinder, and the exhaust-steam goes into he steam-chest and out by theexhaust-ports My improved valve D has a middle part, open at top andbottom, but incloscd laterally all around by Walls d d1 d'2 d3. I husfar the valve is believed to be old. Above it is a relief or balancing'plate, l), having rabbeted edges, as shown, which underlie the edges ofa hole made in the top plate A2 of the steamchest. The upper face of thebalancing-plate Pis, by preference, made so as, in its usual position,to be about flush with the upper or outer face of the steam-chest cover,so as to permit of the use of a ilexible gasket or plate, c, whichoverlaps the joints, and is secured at its 'edges outside the joints bya cover, n, chambered out on its under side, as at u. The gasket cconsists of a thin plate of copper, or other suitable material, and itselasticity is such, and the construction of the plate P is such, thatthe latter may have a slight vertical motion oi', say, the one-sixteenthof an inch, more or less. A hole, el, is made ceutrally through thebalancing-plate P for the admission of live steam to the chamber u', andthe gasket is fastened down around the hole by a washer and screws, asshown at c2.

The parts described are so proportioned that the area of surface on theunder side of the balancing-plate P subject to steam-pressure throughthe open top of the valve shall be somewhat less than the area of itsupper surface included within the chamber n subject to downwardsteam-pressure, so that, in the manner well known in the art, the valvewill be held down to its seat with the proper degree or amount of forceor pressure. The rules governing this are too well known to skilledengine-builders to need further statement.

Further features of improvement are design ed to obviate certainpractical difficulties, which I have found to exist in this class ofbalanced valves. First, when the valve begins a stroke either way, onefoot or lower face of the valve commences to eut oft' the supply of livesteam to one end of the cylinder. lVhile that part of the valve ispassing that particular port, the expansive force of th e steam, actingback through the port, tends to lift that end ofthe valve and thus tiltit on its transverse axis, thus causing it to leak and `subject thegasket e to an irregular breaking-strain. To remedy this, I lengthen thevalve D by-extending its side walls at each end, as at e, and, bypreference, connect the extreme upper and lower faces of the endextensions e by means of cross-bars e', and make the upper face of theupper bar and extension and the lower face of the lower bar andextension preferably in the plane of the upper L,and lower valvefaces,respectively.

The extensions thus formed bear on the valveseat below while the valveis subjected to the vlifting effect referred to on the balancingplateabove, or ou the extended edge of the same, and outside of the verticalplane of the upward pressure. Such extension ofthe valve,

in its relation to the bearing-surfaces, has the l effect to prevent orlessen the tilting referred to, in accordance'with principles ofleverage well understood in mechanics.

Another practical difficulty which I obviate results from the upwardpressure of the valve ends, already referred to, against the ends of thebalancing-plate, which, in addition to evils already mentioned, causesundue friction and cutting at such points. To prevent or lessen this, Ipack or cushion the upper faces of the valve ends while passing theports on return strokes by means of live steam. For this purpose I makerecesses s s' in the lower face of the balancing-plate I), one directlyover the mouth of each port ay a, and of about the same arca.

As shown in Fig. 1, while the port a is takin g steam the recess s willalso be filled with live steam, or steam under expansion. As the valvemakes its return stroke and comes to the position shown in Fig. 2, itwill cut off steam from a', and also will confine a small quantity oflive steam in the recess s', the effective downward pressure of whichwill nearly or exactly counterbalance the upward pressure of steamagainst the bottom of the valve through the port a. IIence the effect ofback-pressure on the valvefoot will. be wholly eliminated, or, bylessening the area of the recess, partially so, as may be preferred.Also, by enlarging such recess and giving the top of the valve a greaterlap thereon, a slight preponderance of downwardpressure can be secured,when desired. After the valve passes the recess, the steam confinedtherein goes to the exhaust. The same operation takes place at the otherend of the valve on its return stroke, and so on alternately.

Vhile the balancing device thus described is sufficiently secure in itsplace, and, by its connections, to perform with certainty the objectssought, it is also so far free of bolts, clamps, or interloekin g partsas to adapt itself readily to all the varying conditions of use. 'Forexample, if it be necessary to reverse the engine while taking steam ateither end, dan ger of accident will be materially lessened, from thefact that under the excessive pressure resulting therefrom the 'alve orbalancin g-plate, or both, may lift or yield sufliciently to allow ofenough leakage of steam to prevent explosion or other injury.

Other appliances, as usual with slide-valves, are to be added, such asvalve-stem D', stufiing-box D2, and also other desired devices, notusual, may be added.

The terms top and bottom, upper7 and lower are used herein in a relativesense, so that I do not limit myself in the invention to a horizontallyworking valve arranged in a valve-chest on the upper side of a cylinder.

The object of rabbeting the edge of the bal ancing plate is, in part, tolimit the possible upward movement of the plate, and partly to lessenthe possible limit of its tilting motion, and at the same time renderthe construction more compact.

The slide-valve shown and described also diers from other valves inother respects of like construction, in that the steam is exhaustedendwise between the cross-bars, which, as shown, constitute a part ofthe end extension.

I make no claim of exclusive right to anything vshown or described ineither of the patents granted to John Baird, April 5, 1864, or GeorgeRieseck, March 31, 1863.

In my improvement it will be observed that the end extension of avertically-moving balancing-plate, in combination with the end extensionof the valve, presents both novelty a-nd utility in a patentable sense,since the plate thereby better prevents the lifting of the end of thevalve, while the balaliciiigeii'eet is still secured.

I claim herein as my invention- I'. The balancing-plate I, working likea piston, with a slight range of motion, through a hole in the top plateof the steam-chest, and with its lower surface underlying the edges ofthe hole in the top plate, in combination with a slide-valve having abearing-extension at each end beyond the valve foot proper, whereby thebalancing-plate, while free to perform its function as such, also bearson the whole, or nearly the whole, upper surface ol.' the valve when thelatter is at the ends as well as at the middle of its stroke,substantially as set forth.

2. The balancing-plate I?, working in the top plate ofthe steam-chest,as described, and overlapping the end extensions of the valve, asdescribed, and having a steam-port through or past the same, incombination with a flexible gasket to cover the joint of thebalancingplate and cover, and also in combination with a valve having anopen top and end extensions, substantially as set forth.

3. The balancing-plate I), having a slight vertical, but nolongitudinal, lnotion, made with a hole through or past the same, andrecesses s s in its lower face, immediately over the open ends or mouthsof the cylinder-ports, in combination with the described valve andgasket, substantially as set forth.

4. The valve D, having the end extensions described, in combination withcentral steamport B, end exhaust-ports I3 B', and balancing-plate I),having end extensions, substantially as set forth.

5. A slide-valve having a bearing-extension at each end, which projectsbeyond the valve-foot proper, and having also an end opening throughsuch extension for an endwise exhaust from the valve, substantially asset forth.

In testimony whereof I have hereunto set my hand.

JOHN C. BRYAN.

Witnesses:

J. J. McGonMicK, CLAuDiUs L. PARKER.

